Two '67 L71 questions:

[Norris W.]

First: Overheat/damage. A little background. I bought an ole' mud bogger in the 80's with a '67 435 block in it and went and found the car and bought it a coupla' years later. When found, the car had a '68 dated CE shortblock assembly in it with the original heads, manifolds etc. I never saw any reason in the original block where it was replaced under warranty. I've driven the car only occasionally and it's usually trailered to an out of town event somewhere and the trips have been short. Last fall, when driving to a local car show and encountering traffic it got very hot and being within a block I continued and when parked it left a car size antifreeze deposit on the ground. I didn't crank it again and after letting it sit for 6 or 7 hours went and got the trailer and cranked the car only to load it. The oil level was high and I got it in my mind I'd popped the head gaskets. I decided yesterday to get two of my "non runners" back up and going and pumped up the radiator on the Corvette and it stayed at 14 PSI for several hours. Overnight, about 12 hours later it has lost down to about 8 lbs on the gauge. Obviously head gaskets I don't think would hold at all, so I'm wondering if I've got a crack somewhere that opens with heat or if I'm "making oil" for some other reason, like fuel. I can't recall if the oil looked milky at all last year, but after sitting for several months the oil on the dipstick looks like recently changed. Although I don't see any external water leaks from the overnight pressure it occurs to me that there is possibility that the guage/pump assembly itself could possibly lose some pressure overnight. Opinions?????

Second: The car has always been very hard to start after cutting off until it sits for a while. It's always appeared rich, smelled rich and the rear tires are even ****ty in the redlines from the side exhaust. A friend who recently bought an L71 off the internet soon experienced a fuel pump failure and replaced it with a supposedly correct AC Delco piece from a reputable supplier. He had similar hard start and "making oil" issues and his mechanic, more of a late model car guy started with basics including checking fuel pressure and determined that the pump was putting out over 9 PSI and overwhelming the needles/seats. I was skeptical, but they replaced the pump with an el cheapo O'Reilley's part that was less than 6 PSI and the hard start and extra oil issues went away. I've put kits in my carbs myself, and later had a well known carb resto shop who's done a lot of stuff for us completely do 'em including the finish. The car has always had these characteristics since I built the engine complete with a new at the time Delco fuel pump. So the question is, has anyone else had issues with high fuel pressure on these pumps and what's a reasonable solution other than going to an aftermarket pump that doesn't look anywhere near correct?

I guess I'm kinda' graspin' at straws here because I don't want to pull this engine with all the other projects that need attention.

[Patrick B.]

[John D.]

Re: Two '67 L71 questions:

Would a compression test or cylinder leakdown test help ?

[Norris W.]

Re: Two '67 L71 questions:

I wish there was a way to limit the pressure to the carbs without an obvious external filter. Obviously in any carb volume is what matters and pressure is irrelevant as long is it's sufficient to move the volume. We found that out years ago on our outboard race boats and I started regulating mine to 3 PSI and the low speed manners improved drastically. Strange how Chevy used return lines on some SHP engines but not on others. Patrick it's been sitting long enough now that there wouldn't be any residual gas in the cyl's. John, I've got both compression and leakdown testers, but this engine hasn't got over 2 or 300 miles on it since +.030 and completely freshened, so doubt I'd have an issue there. I guess the best thing to do is drain the oil and have a look. If no water present just assume it's gas and figure out a way to solve that. In all these years I've never tested fuel pressure on a stock type mechanical pump but if that's an issue it sure would answer a lot of questions on several tri power cars.

[Danny P.]

Re: Two '67 L71 questions:

I wish there was a way to limit the pressure to the carbs without an obvious external filter. Obviously in any carb volume is what matters and pressure is irrelevant as long is it's sufficient to move the volume. We found that out years ago on our outboard race boats and I started regulating mine to 3 PSI and the low speed manners improved drastically. Strange how Chevy used return lines on some SHP engines but not on others. Patrick it's been sitting long enough now that there wouldn't be any residual gas in the cyl's. John, I've got both compression and leakdown testers, but this engine hasn't got over 2 or 300 miles on it since +.030 and completely freshened, so doubt I'd have an issue there. I guess the best thing to do is drain the oil and have a look. If no water present just assume it's gas and figure out a way to solve that. In all these years I've never tested fuel pressure on a stock type mechanical pump but if that's an issue it sure would answer a lot of questions on several tri power cars.

Hi Norris, I think what going on is your sucking down fuel from your metering plate how long ago has your Carbs. been rebuild , has anyone check the metering plate and the housing for warpage and if the wrong meter plate gasket is used it would cause vacuum draw and drain fuel down the intake , just a thought

[Mark E.]

Re: Two '67 L71 questions:

Hi Norris, I think what going on is your sucking down fuel from your metering plate how long ago has your Carbs. been rebuild , has anyone check the metering plate and the housing for warpage and if the wrong meter plate gasket is used it would cause vacuum draw and drain fuel down the intake , just a thought

Along that line- If the "oil" level is increasing it's either fuel or coolant:
- Fuel- From the carburetor or fuel pump
- Coolant- Intake manifold or head gasket

None of these would show up on a leak down or compression test. A cracked block is less likely. Coolant on the ground after a hot shut down is normal.

Check the oil to see what's in it and go from there.

[Daniel Y.]

Re: Two '67 L71 questions:

Norris, I too had bought a fuel pump from a reputable supplier - Goat Hill in California. I had bought 2 others before and never had an issue. I had similar issues with a rich smell and hard start, not a stable idle. I asked my carb rebuilder ( he has always been great - Custom Carbs in Middlesex, NJ). He said before you adjust ANYTHING. check the fuel pressure. I told him I doubt that would be a problem since I had bought the same carb from the same vendor. He was adamant. so I ordered the parts to check the fuel pressure. GUES WHAT? it was pushing out 9 PSI. Its should be between 5&6 PSI. I ordered one on ebay that has a good rep. installed and its pushing 5 PSI - perfect. Interestingly - he had no idea what the PSI was. I replaced the needle and seats, checked the float levels. and everything starts and runs perfectly!
if you haven't done so already, check the fuel pressure